This invention relates to apparatus for applying dyes to webs so as to obtain a smoothly changing gradation in the amount of dye present on the web as a function of the distance from a specified edge.
There are currently commercially available glass lenses which have been dyed with a gradation in shade from a deep hue, generally at the top of a lens, vignetting to a very light hue as the dye area nears the bottom of the lens. The lenses for such sunglasses are usually prepared by dipping each lens slowly into a dye material and removing the lens so dipped. The result of this individual dipping is a differential dyeing as a function of the residence time of each lens in the dye solution, but the process is a slow and expensive one.
The object of this invention is to provide a means for the continuous production of a web material having a predetermined dye density gradient. The web may be cut into sunglass lenses after the dyeing process.
Another object is to provide the means for assuring a requisite differential residence time in the dye bath without introducing striations which mark the limit of dye contact.
A still further object is to provide apparatus useful in the continuous preparation of a web with a dye density gradient.
Other objects of the invention will in part be obvious and will in part appear hereinafter.
The invention accordingly comprises the apparatus possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure.